Tropical Storm HAGIBIS Advisory Вс, 06.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (HAGIBIS)
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 20W (HAGIBIS), LOCATED APPROXIMATELY 755 NM
EAST OF ANDERSEN AFB, GUAM, HAS TRACKED WESTWARD AT 15 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION WITH IMPROVED SPIRAL
BANDING, INTENSE VORTICAL HOT TOWERS AND A DEVELOPING CENTRAL DENSE
OVERCAST FEATURE OBSCURING THE CENTER. A 051829Z SSMIS 91GHZ COLOR
COMPOSITE IMAGE, HOWEVER, SHOWS A PARTIALLY-EXPOSED, DEFINED CENTER
WITH TIGHTLY-CURVED SHALLOW BANDING OVER THE NORTHERN SEMICIRCLE AND
DEEP CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE, WHICH SUPPORTS
THE CURRENT POSITION WITH FAIR CONFIDENCE. UPPER-LEVEL ANALYSIS
INDICATES NEAR-RADIAL OUTFLOW WITH LOW VERTICAL WIND SHEAR. SST
VALUES OF 30-31C AND HIGH OCEAN HEAT CONTENT VALUES ALSO SUPPORT
SIGNIFICANT INTENSIFICATION. THE CURRENT INTENSITY IS ASSESSED AT 35
KNOTS BASED ON A PGTW DVORAK INTENSITY ESTIMATE OF T2.5 (35 KNOTS),
CONSISTENT WITH A 05/1740Z ADT ESTIMATE OF T2.4. THE SYSTEM IS
TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL
RIDGE (STR) ENTRENCHED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE. ADDITIONALLY, THIS
FORECAST REMAINS HIGHLY CONSISTENT WITH THE PREVIOUS JTWC FORECAST.
   B. TS 20W IS FORECAST TO TRACK WESTWARD TO WEST-NORTHWESTWARD
THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE STR.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN VERY FAVORABLE
THROUGH THE FORECAST PERIOD WITH ROBUST OUTFLOW, WARM SST AND HIGH
OCEAN HEAT CONTENT VALUES SUPPORTING PERIODS OF RAPID
INTENSIFICATION (RI). JTWC INTENSITY GUIDANCE INDICATES A HIGH
PROBABILITY OF RI THROUGH TAU 48, BEFORE THE SYSTEM HITS THE
NORTHERN MARIANAS. THIS FORECAST INDICATES A TYPHOON-STRENGTH SYSTEM
(70-80 KNOTS) IMPACTING THE NORTHERN MARIANAS, HOWEVER, THERE IS
UNCERTAINTY IN THE EXACT INTENSITY WITH POTENTIAL FOR A STRONGER
SYSTEM. OVERALL, THERE IS MODERATE CONFIDENCE IN THE JTWC TRACK
FORECAST THROUGH TAU 48 WITH AN 83 NM SPREAD IN SOLUTIONS AT TAU 48.
   C. IN THE EXTENDED PERIOD, TS 20W WILL GENERALLY TRACK WEST-
NORTHWESTWARD TO NORTHWESTWARD TOWARD A BREAK IN THE STR ASSOCIATED
WITH A DEEP, DYNAMIC SHORTWAVE TROUGH FORECAST TO DEEPEN OVER
WESTERN JAPAN. IMPROVED POLEWARD OUTFLOW ASSOCIATED WITH THIS
SHORTWAVE TROUGH WILL AID IN BOOSTING THE INTENSITY TO SUPER TYPHOON
STRENGTH. THERE IS INCREASING UNCERTAINTY AFTER TAU 96 AS THE
NUMERICAL MODEL GUIDANCE DIVERGES WITH A 385 NM SPREAD IN SOLUTIONS
AT TAU 120. THE PRIMARY OUTLIER IS GFS (AVNI), WHICH IS RECURVING
THE SYSTEM EARLIER AND MORE AGGRESSIVELY INTO THE STR. THE REMAINING
GUIDANCE IS IN FAIR AGREEMENT WITH A SPREAD OF 250 NM AT TAU 120.
THE ECMWF ENSEMBLE ALSO INDICATES A SIMILAR SPREAD OF ITS ENSEMBLE
MEMBERS. OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST
DUE TO THE LARGE SPREAD IN THE MODEL GUIDANCE IN THE EXTENDED PERIOD
REFLECTING UNCERTAINTY IN THE TIMING OF THE RECURVE.//
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